import java.util.*;
public class a {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long a = sc.nextLong();
        long b = sc.nextLong();
        long c = sc.nextLong();

        //计算周数
        long week = c / (a * 5 + b * 2);
        //不满一周的部分
        long last = c % (a * 5 + b * 2);

        //计算不满一周的部分需要几天完成
        int i;
        for (i = 1; last > 0; i++) {
            if (i < 6) {
                last -= a;
            } else {
                last -= b;
            }
        }
        System.out.print(week * 7 + i - 1);
    }
}
